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Should geoengineering be used to address global warming?

If humans heated the earth, perhaps our technology can cool it, too. A look at the science of geoengineering and how it might be used to address global warming.

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Mimicking this "volcano effect" could produce rapid cooling, although sulfur particles would have to be sent into the atmosphere on a regular basis to maintain the effect. If the program had to be discontinued, the cooling effect would quickly wear off and warming would spike upward.

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Because SRM options don't actually remove CO2 from the air, they also don't address global warming's so-called evil twin: ocean acidification. As levels of CO2 in the atmosphere rise, more CO2 is absorbed by oceans, making them more acidic. If acid levels rise enough, coral reefs and shellfish could die off. Eventually, the entire oceanic food chain could be threatened.

All geoengineering fixes present the possibility of unexpected problems, says Michael MacCracken, chief scientist for climate-change programs at the nonprofit Climate Institute in Washington. Each solution will have downsides. "There's no such thing as a free lunch," he says. "There's just different lunches."

That's why "daring to go in and change the climate is something that someone has to be very cautious and careful and humble about," he says,

Efforts to regulate how geo­engineering would be tested – let alone employed – are in their infancy, says David Victor, a political scientist at the University of California at San Diego who studies international environmental regulation.

"I think the problem is that the geoengineering technologies are all over the map, so nobody is really sure where these efforts would begin," he says.

For example, the idea of dumping iron particles at sea to increase its ability to grow more algae that would in turn absorb more CO2 may be regulated to some degree by existing international laws, Dr. Victor says. "It's clear that dumping stuff in the oceans willy-nilly is outside what is legal."

But many SRM techniques present a legal "blank slate," he says. "In my view, the really tough [legal] issues arise from tinkering with the sun, with incoming solar radiation."

While some research, such as computer models, can be done in the laboratory, real-world testing eventually would have to be done. Scientists learned the effects of nuclear bombs on the atmosphere, for example, only when they observed actual test explosions, he points out.

While testing does pose risks, transparent research – in which test results and data are freely and openly shared among the world's scientists and overseen by governments – presents the best way forward, some say.

The alternative is that unscrupulous research might go on "in the shadows," Victor says. "You want to lay down a pattern of behavior" now, he argues, one that sets out what is acceptable – and what isn't.

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